Case report of an alleviation of pain symptoms in hypnic headache via greater occipital nerve block

Introduction

Hypnic headache is a rare primary headache disorder included in the International Classification of Headache Disorders, third edition beta (ICHD-III beta) (1). The clinical features consist of recurrent headache attacks, which occur exclusively during sleep, causing wakening and lasting up to four hours. Its usual onset is after the age of 50. The pain is dull and aching but can as well be sharp, throbbing and even burning with intensity lasting from light to moderate in two-thirds and severe in one-third of the patient population (2,3). Most headache attacks occur between 2 a.m. and 4 a.m. According to ICHD-III-beta cranial nerve autonomic symptoms and restlessness are unusual and should be ruled out before diagnosing hypnic headache. Based on a recent review there are just a few hundred described cases in medical history so far (3). The pathophysiology behind this rare headache disorder remains unknown but hypothalamic involvement is assumed (4). Being a relatively rare disease, therapeutic approaches are mostly derived from case reports and experience. There are no randomised, controlled clinical trials. For acute therapy caffeine seems to be a useful drug as there are consistent reports of pain alleviation after self-administration of caffeine usually in the form of coffee. As prophylactic medication lithium, caffeine, topiramate and indomethacin are of limited to moderate effect in pain control and prevention (3,5). Numerous other drugs have been tried (e.g. Table 1) but none could provide sufficient relief or induce remission. Another approach to treat primary headache disorders are occipital nerve blocks. As described by Blumenfeld et al., there is proven effectiveness in migraine headache, cluster headache and chronic daily headache (5).

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Table 1.

Summary of unsuccessful medication (maximum daily dose, duration and side effects).

Substance	Maximum daily dose	Duration of intake	Side effects
Lithium	900 mg	Eight weeks	None
Indomethacin	200 mg	Six weeks	None
Flunarizine	10 mg	Eight weeks	Drowsiness
Melatonin	2 mg	Eight weeks	None
Topiramate	250 mg	Six weeks	Cognitive impairment
Tapentadol	200 mg	Eight weeks	Drowsiness during daytime and nausea

Case

A 74-year-old female patient was diagnosed with hypnic headache in our headache outpatient department. She reported her condition had already been in existence five years prior to our first contact. She described 45- to 60-minute lasting headache attacks which occur every night at around 2:30–3:00 a.m. The pain usually begins in the left supraorbital region wanders over the scalp towards the neck and occipital region, and is described as a dull and aching. She reported a light restlessness during attacks and no cranial nerve autonomic symptoms. After self-medication with up to three cups of coffee the attack can usually be abbreviated to 45 to 60 minutes. Without coffee an attack could last up to four hours. In our physical examination there was no sign of neurologic or cardiovascular impairment. After ruling out secondary headache diseases via magnetic resonance imaging (MRI) scan, a dentist consultation, and an ear, neck and throat evaluation, we classified the medical condition as hypnic headache. Our therapeutic approaches with effects and side effects are summarised in Table 1.

Methods

Due to the fact that our patient didn’t respond to any oral medication, we decided to try an occipital nerve injection therapy. A mixture of 5 ml of bupivacaine and 40 mg of triamcinolone was injected 1–2 cm below the midpoint between the occipital tubercle and the mastoid process on both sides. After the injection the area was gently rubbed to distribute the triamcinolone to affect a larger part of the greater occipital nerve (GON).

Results

The patient was reevaluated one week after the first injection. She reported a shift in her pain onset from 3 a.m. to 4 a.m. towards 6 a.m. and a reduction in pain intensity. A second occipital nerve injection was performed two weeks after the first one. The patient reported that she was pain free the following six days after the second injection. After one week the pain returned at less intensity. Over the course of six months the patient described during monthly follow-ups a stable situation with a reduced frequency of one to two times a week with a slight shift in time of onset between 5 a.m. and 6 a.m.

Discussion

To our knowledge this is the first time that a GON block has been used as a treatment for hypnic headache.

As the pathophysiology of hypnic headache still remains unclear, there is no obvious explanation why the GON block provided a successful treatment. GON blocks provide pain relief in many primary headache disorders as well as cluster headache (6,7).

The GON is a branch of the second cervical nerve and there is a convergence between cervical and trigeminal nerve afferent inputs in cranial nociception (8,9). These convergent inputs lead to a ‘functional continuum between the caudal trigeminal nucleus and upper cervical segments involved in cranial nociception’ as reported by Bartsch and Goadsby (10).

An alteration of trigeminal nociceptive blink reflex latencies after peripheral nerve blockade of the ipsilateral occipital nerve could be demonstrated as well, which further fortifies a functional connection between cervical nerves and central trigeminal pain transmission (11).

The trigeminal nerve takes part in a broad range of primary headache disorders. This gives evidence that occipital nerve blockade is able to alter peripheral pain reception transmitted through the trigeminal nerve nucleus. Although there is yet no clear pathophysiological explanation for hypnic headache attacks, we hypothesise that there has to be trigeminal nerve involvement as GON block showed a significant pain reduction in our case.

However, we did not observe a permanent cure nor a complete remission of the experienced pain, rather a significant reduction of frequency as well as a shift of onset and intensity of the pain attacks. We could observe a stable effect over the duration of six months that exceeds the medical effect of the used corticosteroid triamcinolone. Altered central pain processing via alteration of trigeminal nerve afferent inputs could be possible.

As another explanation the placebo effect should not be underestimated as the received treatment provided a much more invasive approach than oral medication and an ‘experimental setting’ which could act as a strong psychological influence on pain perception and presentation. We hypothesise that the persistent effect of pain reduction and health-related quality of life for our patient for at least six months cannot be singlehandedly explained by placebo effects but in future studies there should be placebo-controlled trials of GON blockades in hypnic headache disease.

The GON blockade is a relatively simple, less invasive and easy to learn method which has just a few side effects. The main effects are described as local alopecia and skin atrophy on the side of injection, which seldom occur (12).

Therefore, we suggest a therapeutic trial for patients who did not benefit from standard oral medication. Whether GON blockade provides an additive pain control effect when administered in combination with oral treatment or earlier in the therapeutic course is an interesting question that also needs further investigation.

Clinical implications

In summary, this case report could show that a greater occipital nerve (GON) block can significantly alleviate pain symptoms in hypnic headache if oral medication fails. GON block is a safe and easy to learn method with just a few side effects. Due to known trigeminal nerve convergence of craniocervical nerve roots and trigeminal afferences, we also hypothesise that there may be trigeminal nerve involvement in hypnic headache.